大乘起信論義記 2.217

2.217

初言智相者，謂於前現識所現相上，不了自心現故，始起慧數分別染淨執有定性，故云依於境界乃至不愛故也。

First, as for "the mark of cognition": upon the marks manifested by the preceding manifesting consciousness, failing to understand that they are the manifestation of one's own mind, the mental factor of discernment initially arises to differentiate defilement and purity and grasp them as having fixed natures; hence it says, "based on objects... between the pleasant and the unpleasant."